Ambient air pollution and adverse birth outcomes: a systematic review and meta-analysis

Urban environment and children's health: An umbrella review of exposure response functions for health impact assessment

BACKGROUND

Urban settlements have become the main living environment. Understanding the impact of urban exposures on human health has therefore become a growing area of research. Up-to-date knowledge about the influence of urban exposures on pregnant women's and children's health is especially relevant, as they are particularly vulnerable to certain external influences.

AIM

This review aims to provide a synthesis of systematic reviews with meta-analyses reporting on an association between the urban environmental risk factors and health outcomes in pregnancy, infants, children and adolescents.

METHODS

We conducted an umbrella review, methodically analysing systematic reviews with meta-analyses, published between January 2016 and December 2022 in PubMed or Scopus. Adhering to the PRISMA checklist, we searched for free text using Medical Subject Headings (MeSH) terms related to air pollution, noise pollution, temperature, green space exposure, built and food environment, health outcomes, children (aged 0-18 years), pregnancy and systematic reviews with meta-analyses. We extracted key characteristics of each included study and assessed the quality of the included studies via the R-AMSTAR 2 tool.

RESULTS

Twenty-four studies met our inclusion criteria and identified 104 associations including 15 exposures and 60 health outcomes. The most frequently studied associations were related to air pollutants, followed by the built and food environment and noise. Birth outcomes (including low birth weight, pre-term birth or stillbirth) were the most commonly affected health outcomes, followed by respiratory outcomes such as asthma or respiratory infections. A total of 45 exposure-response function were reported to be statistically significant, including 10 exposures and 23 health effects.

CONCLUSION

This umbrella review provides an overview of the evidence and availability of exposure response functions between selected urban exposures and child health outcomes. This helps to identify research gaps and to build the basis for health impact assessment.

Meta-analysis of fine particulate matter exposure during pregnancy and birth weight: Exploring sources of heterogeneity

BACKGROUND

Several meta-analyses assessed the relationship between exposure to PM with aerodynamic diameter ≤ 2.5 μm (PM2.5) during pregnancy and birth weight (BW), but results were inconsistent and substantial unexplained heterogeneity was reported. We aimed to investigate the above association and to explore sources of heterogeneity across studies.

METHODS

We systematically reviewed the current worldwide evidence examining the association between PM2.5 and BW. The review protocol was registered on the PROSPERO website (CRD42020188996) and followed PRISMA guidelines. We extracted association measures for BW and low birth weight (LBW, BW < 2500 g) from each study to evaluate pooled summary measures and to explore sources of between-study heterogeneity.

FINDINGS

Of the 2677 articles identified, 84 met the inclusion criteria (~42 M births). Our random effects meta-analyses revealed substantial heterogeneity among included studies (I2 = 98.4 % and I2 = 77.7 %, for BW and LBW respectively). For LBW, the heterogeneity decreased (I2 = 59.7 %) after excluding four outlying studies, with a pooled odds ratio 1.07 (95 % confidence interval, CI: 1.05, 1.09) per a 10-μg/m3 increase in mean PM2.5 exposure over the entire pregnancy. Further subgroup analysis revealed geographic heterogeneity with higher association in Europe (1.34, (1.16, 1.55)) compared to Asia (1.06, (1.03, 1.10)) and US (1.07, (1.04, 1.10)).

CONCLUSION

The association between PM2.5 and birth weight varied depending on several factors. The sources of heterogeneity between studies included modifiers such as study region and period. Hence, it is advisable not to pool summary measures of PM2.5-BW associations and that policy would be informed by local evidence.

Pre-pregnancy ozone and ultrafine particulate matter exposure during second year of life associated with decreased cognitive and adaptive functioning at aged 2-5 years

BACKGROUND

This study sought to investigate the association of prenatal and early life exposure to a mixture of air pollutants on cognitive and adaptive outcomes separately in children with or without autism spectrum disorder (ASD).

METHODS

Utilizing data from the CHARGE case-control study (birth years: 2000-2016), we predicted daily air concentrations of NO2, O3, and particulate matter <0.1 μm (PM0.1), between 0.1 and 2.5 μm (PM0.1-2.5), and between 2.5 and 10 μm (PM2.5-10) using chemical transport models with ground-based monitor adjustments. Exposures were evaluated for pre-pregnancy, each trimester, and the first two years of life. Individual and combined effects of pollutants were assessed with Vineland Adaptive Behavior Scales (VABS) and Mullen Scales of Early Learning (MSEL), separately for children with ASD (n = 660) and children without ASD (typically developing (TD) and developmentally delayed (DD) combined; n = 753) using hierarchical Bayesian Kernel Machine Regression (BKMR) models with three groups: PM size fractions (PM0.1, PM0.1-2.5, PM2.5-10), NO2, and O3.

RESULTS

Pre-pregnancy Ozone was strongly negatively associated with all scores in the non-ASD group (group posterior inclusion probability (gPIP) = 0.83-1.00). The PM group during year 2 was also strongly negatively associated with all scores in the non-ASD group (gPIP = 0.59-0.93), with PM0.1 driving the group association (conditional PIP (cPIP) = 0.73-0.96). Weaker and less consistent associations were observed between PM0.1-2.5 during pre-pregnancy and ozone during year 1 and VABS scores in the ASD group.

CONCLUSIONS

These findings prompt further investigation into ozone and ultrafine PM as potential environmental risk factors for neurodevelopment.

Ambient fine particulate matter and pregnancy outcomes: An umbrella review

The available evidence on the effects of ambient fine particulate matter (PM2.5) and pregnancy outcomes (birth outcomes and pregnancy complications) has increased substantially. The purpose of this umbrella review is to refine the evidence of the association between birth outcome (birth defects) and PM2.5; and summarize the credibility of existing research on the association between pregnancy complications and PM2.5. We searched PubMed, Web of Science, Embase, and Cochrane databases for relevant systematic reviews and meta-analyses up to March 16, 2022 in accordance with PRISMA guidelines. Two independent investigators conducted data extraction. AMSTAR 2 and GRADE assessment criteria were used to evaluate the methodological and evidence quality. We performed subgroup analyses by trimesters of pregnancy. The review protocol for this study has been registered in PROSPERO (CRD42022325550). This umbrella review identified a total of 41 systematic reviews, including 28 articles evaluating the influence of PM2.5 on birth outcomes and 13 on pregnancy complications. Positive associations between perinatal PM2.5 exposure and adverse birth outcomes were found, including low birth weight, preterm birth, stillbirth, small for gestational age, and birth defects. Pregnant women exposed to PM2.5 had a significantly higher risk of developing hypertensive disorder of pregnancy, gestational diabetes mellitus, gestational hypertension, and preeclampsia. The findings of subgroup analysis demonstrated that the effects of ambient PM2.5 exposure on pregnancy outcomes varied by trimesters. The findings of this extensive umbrella review provide convincing proof that exposure to ambient PM2.5 raises the risks of unfavorable birth outcomes and pregnancy complications. Some associations show considerable disparity between trimesters. These findings have implications for strengthen perinatal health care on air pollution and improving intergenerational equity.

The protocol of DECO-MOM: a clinical trial testing the effectiveness of a mobile application for an environmental health intervention among pregnant women

BACKGROUND

Environmental toxins are particularly harmful to pregnant women and their fetuses due to the long-term effects of these toxins on children after birth. Environmental health behaviors can prevent and protect mothers and their babies' environmental health.

METHODS/DESIGN

This study presents a protocol for a double-blinded randomized controlled trial to examine the effect of a mobile application named "DECO-MOM" (Deep ECOlogy-MOM) for pregnant women. This application contains content related to environmental perceptions and behaviors according to the revised protection motivation theory. The mobile intervention will be implemented for 4 weeks for 40 pregnant women with a gestational age in the first trimester. As the control group, 40 pregnant women will be recruited at public healthcare centers in Chuncheon and Gongju in South Korea. The hypothesis is that the experimental group will have higher scores for environmental perceptions and behaviors than the control group. An online survey administered before and after the intervention will contain outcome parameters including depression, stress, quality of life, e-learning satisfaction, environmental perceptions, and environmental behaviors.

DISCUSSION

This study will elaborate a guide for an intervention to enhance the effects of the mobile application on strengthening environmental health perceptions, behaviors, e-learning satisfaction, and quality of life and curtailing depression and stress among pregnant women.

TRIAL REGISTRATION

Trial registration Number: KCT0007725, Registered September 22, 2022. Prospectively registered.

Impact of ambient air pollution exposure during pregnancy on adverse birth outcomes: generalized structural equation modeling approach

BACKGROUND

Air pollution and several prenatal factors, such as socio-demographic, behavioural, physical activity and clinical factors influence adverse birth outcomes. The study aimed to investigate the impact of ambient air pollution exposure during pregnancy adjusting prenatal risk factors on adverse birth outcomes among pregnant women in MACE birth cohort.

METHODS

Data for the study was obtained from the Mother and Child in the Environment (MACE) birth cohort study in Durban, South Africa from 2013 to 2017. Land use regression models were used to determine household level prenatal exposure to PM_2.5, SO₂ and NOx. Six hundred and fifty-six births of pregnant females were selected from public sector antenatal clinics in low socio-economic neighbourhoods. We employed a Generalised Structural Equation Model with a complementary log-log-link specification.

RESULTS

After adjustment for potential prenatal factors, the results indicated that exposure to PM_2.5 was found to have both significant direct and indirect effects on the risk of all adverse birth outcomes. Similarly, an increased level of maternal exposure to SO₂ during pregnancy was associated with an increased probability of being small for gestational age. Moreover, preterm birth act a mediating role in the relationship of exposure to PM_2.5, and SO₂ with low birthweight and SGA.

CONCLUSIONS

Prenatal exposure to PM_2.5 and SO₂ pollution adversely affected birth outcomes after controlling for other prenatal risk factors. This suggests that local government officials have a responsibility for better control of air pollution and health care providers need to advise pregnant females about the risks of air pollution during pregnancy.

Household polluting cooking fuels and adverse birth outcomes: An updated systematic review and meta-analysis

Background and aim

The current study aimed to clarify the association between household polluting cooking fuels and adverse birth outcomes using previously published articles.

Methods

In this systematic review and meta-analysis, a systematic literature search in PubMed, Embase, Web of Science, and Scopus databases were undertaken for relevant studies that had been published from inception to 16 January 2023. We calculated the overall odds ratio (OR) and 95% confidence interval (CI) for adverse birth outcomes [low birth weight (LBW), small for gestational age (SGA), stillbirth, and preterm birth (PTB)] associated with polluting cooking fuels (biomass, coal, and kerosene). Subgroup analysis and meta-regression were also conducted.

Results

We included 16 cross-sectional, five case-control, and 11 cohort studies in the review. Polluting cooking fuels were found to be associated with LBW (OR: 1.37, 95% CI: 1.24, 1.52), SGA (OR: 1.48, 95% CI: 1.13, 1.94), stillbirth (OR: 1.38, 95% CI: 1.23, 1.55), and PTB (OR: 1.27, 95% CI: 1.19, 1.36). The results of most of the subgroup analyses were consistent with the main results. In the meta-regression of LBW, study design (cohort study: P < 0.01; cross-sectional study: P < 0.01) and sample size (≥ 1000: P < 0.01) were the covariates associated with heterogeneity. Cooking fuel types (mixed fuel: P < 0.05) were the potentially heterogeneous source in the SGA analysis.

Conclusion

The use of household polluting cooking fuels could be associated with LBW, SGA, stillbirth, and PTB. The limited literature, observational study design, exposure and outcome assessment, and residual confounding suggest that further strong epidemiological evidence with improved and standardized data was required to assess health risks from particular fuels and technologies utilized.

IS THERE A RELATIONSHIP BETWEEN COMPLICATIONS OF EARLY PREGNANCY AND BIOMETEOROLOGICAL FORECAST?

The aim of our study was to connect the possible complications of early pregnancy (miscarriage and symptomatic ectopic pregnancy) up to the 12th week of gestation with biometeorological conditions while assuming a greater number of incidents with an unfavorable biometeorological forecast. We performed a retrospective observational study using medical data of a single medical center of Department of Gynecology and Obstetrics, Sveti Duh University Hospital and meteorological data from the Croatian Meteorological and Hydrometeorological Service in Zagreb. We tracked the number of visits to the gynecology and obstetrics emergency unit on a daily basis during 2017. Days with five or more visits were selected and underwent further analysis, during which the number of miscarriages and symptomatic ectopic pregnancies was noted. The information from the biometeorological forecast was then extracted and added to the database. Our results did not show a statistically significant difference between the groups determined by biometeorological forecast in the number of spontaneous abortions or ectopic pregnancy. Also, statistically significant results did not follow the expected trend of the increasing number of complications related to worse biometeorological forecast, or vice versa, a decreased number of complications with better forecast. Our single-center retrospective analysis of emergency unit visits related to weather conditions did not show a connection between the complications of early pregnancy and biometeorological conditions. However, different results could emerge in future studies. Considering the large and high-quality database collected for this study, efforts in researching the connection between other gynecologic pathologies and weather conditions will be feasible.

Boston Birth Cohort Profile: Rationale and Study Design

In 1998, the Boston Birth Cohort (BBC) was initiated at Boston Medical Center (BMC) in response to persistently high rates of preterm birth (PTB, defined as birth before 37 weeks of gestation) in the US population and the longstanding profound PTB disparity among Black, Indigenous, and people of color (BIPOC). The BBC encompasses two linked study protocols: The Preterm Birth Study serves as the baseline recruitment in the BBC. It aims to address fundamental questions about the causes and consequences of PTB. The study oversamples preterm babies using a case/control study design, in which cases are defined as mothers who deliver a preterm and/or low birthweight baby (<2500 grams regardless of gestational age). Controls are enrolled at a 2:1 control/case ratio and matched by maternal age (±5 years), self-reported race and ethnicity, and date of delivery (± 7 days for case delivery). From inception, it was designed as a comprehensive gene-environmental study of PTB. As a natural extension, the Children's Health Study, under a separate but linked IRB protocol, is a longitudinal follow-up study of the participants who were recruited at birth in the Preterm Birth Study and who continue pediatric care at BMC. This linked model allows for investigation of early life origins of pediatric and chronic disease in a prospective cohort design. The BBC is one of the largest and longest NIH-funded prospective birth cohort studies in the US, consisting of 8733 mother-child dyads enrolled in the Preterm Birth Study at birth, and of those, 3,592 children have been enrolled in the Children's Health Study, with a median follow-up of 14.5 years. The BBC mirrors the urban, under-resourced and underrepresented BIPOC population served by BMC. A high proportion of BBC children were born prematurely and had chronic health conditions (e.g., asthma, obesity and elevated blood pressure) in childhood. The BBC's long-term goal has been to build a large, comprehensive database (epidemiological, clinical, multi-omics) and biospecimen repository to elucidate early life origins of pediatric and chronic diseases and identify modifiable upstream factors (e.g., psychosocial, environmental, nutritional) to improve health across the life course for BIPOC mothers and children.

Boston Birth Cohort profile: rationale and study design

In1998, the Boston Birth Cohort (BBC) was initiated at Boston Medical Center (BMC) in response to persistently high rates of preterm birth (PTB, defined as birth before 37 weeks of gestation) in the US population and the longstanding profound PTB disparity among Black, Indigenous, and people of color (BIPOC). The BBC encompasses two linked study protocols: The PTB Study serves as the baseline recruitment in the BBC. It aims to address fundamental questions about the causes and consequences of PTB. The study oversamples preterm babies using a case/control study design, in which cases are defined as mothers who deliver a preterm and/or low birthweight baby (<2500 grams regardless of gestational age). Controls are enrolled at a 2:1 control/case ratio and matched by maternal age (±5 years), self-reported race and ethnicity, and date of delivery (± 7 days for case delivery). From inception, it was designed as a comprehensive gene-environmental study of PTB. As a natural extension, the Children's Health Study, under a separate but linked Institutional Review Board protocol, is a longitudinal follow-up study of the participants who were recruited at birth in the PTB Study and who continue pediatric care at BMC. This linked model allows for investigation of early life origins of pediatric and chronic disease in a prospective cohort design. The BBC is one of the largest and longest National Institutes of Health-funded prospective birth cohort studies in the United States, consisting of 8733 mother-child dyads enrolled in the PTB Study at birth, and of those, 3592 children have been enrolled in the Children's Health Study, with a median follow-up of 14.5 years. The BBC mirrors the urban, underresourced, and underrepresented BIPOC population served by BMC. A high proportion of BBC children were born prematurely and had chronic health conditions (e.g., asthma, obesity, and elevated blood pressure) in childhood. The BBC's long-term goal has been to build a large, comprehensive database (epidemiological, clinical, and multiomics) and biospecimen repository to elucidate early life origins of pediatric and chronic diseases and identify modifiable upstream factors (e.g., psychosocial, environmental, and nutritional) to improve health across the life course for BIPOC mothers and children.

The acute effect and lag effect analysis between exposures to ambient air pollutants and spontaneous abortion: a case-crossover study in China, 2017-2019

INTRODUCTION

Recent studies demonstrated that living in areas with high ambient air pollution may have adverse effects on pregnancy outcomes, but few studies have investigated its association with spontaneous abortion. Further investigation is needed to explore the acute effect and lag effect of air pollutants exposure on spontaneous abortion.

OBJECTIVE

To investigate the acute effect and lag effect between exposure to ambient air pollutants and spontaneous abortion.

METHODS

Research data of spontaneous abortion were collected from the Chongqing Health Center for Women and Children (CQHCWC) in China. The daily ambient air pollution exposure measurements were estimated for each woman using inverse distance weighting from monitoring stations. A time-stratified, case-crossover design combined with distributed lag linear models was applied to assess the associations between spontaneous pregnancy loss and exposure to each of the air pollutants over lags 0-7 days, adjusted for temperature and relative humidity.

RESULTS

A total of 1399 women who experienced spontaneous pregnancy loss events from November 1, 2016, to September 30, 2019, were selected for this study. Maternal exposure to particulate matter 2.5 (PM_2.5), particle matter 10 (PM₁₀) nitrogen dioxide (NO₂), and sulfur dioxide (SO₂) exhibited a significant association with spontaneous abortion. For every 20 μg/m³ increase in PM_2.5, PM₁₀, NO₂, and SO₂, the RRs were 1.18 (95% CI: 1.06, 1.34), 1.12 (95% CI, 1.04-1.20), 1.15 (95% CI: 1.02, 1.30), and 1.92 (95% CI: 1.18, 3.11) on lag day 3, lag day 3, lag day 0, and lag day 3, respectively. In two-pollutant model combined with PM_2.5 and PM₁₀, a statistically significant increase in spontaneous abortion incidence of 18.0% (RR = 1.18, 95% CI: 1.06, 1.32) was found for a 20 μg/m³ increase in PM_2.5 exposure, and 11.2% (RR = 1.11, 95% CI: 1.03, 1.20) for a 20 μg/m³ increase in PM₁₀ exposure on lag day 3, similar to single-pollutant model analysis.

CONCLUSION

Maternal exposure to high levels of PM_2.5, PM₁₀, NO₂, and SO₂ during pregnancy may increase the risk of spontaneous abortion for acute effects and lag effects. Further research to explore sensitive exposure time windows is needed.

Fetal Exposure to Air Pollution in Late Pregnancy Significantly Increases ADHD-Risk Behavior in Early Childhood

BACKGROUND

Air pollution nowadays has seriously threatened the health of the Chinese population, especially in the vulnerable groups of fetuses, infants and toddlers. In particular, the effects of air pollution on children's neurobehavioral development have attracted widespread attention. Moreover, the early detection of a sensitive period is very important for the precise intervention of the disease. However, such studies focusing on hyperactive behaviors and susceptible window identification are currently lacking in China.

OBJECTIVES

The study aims to explore the correlation between air pollution exposure and hyperactive behaviors during the early life stage and attempt to identify whether a susceptible exposure window exists that is crucial for further precise intervention.

METHODS

Based on the Longhua Child Cohort Study, we collected the basic information and hyperactivity index of 26,052 children using a questionnaire conducted from 2015 to 2017, and the Conners' Parent Rating Scale-revised (CPRS-48) was used to assess hyperactive behaviors. Moreover, the data of air pollution concentration (PM₁₀, PM_2.5, NO₂, CO, O₃ and SO₂) were collected from the monitoring station between 2011 to 2017, and a land-use random forest model was used to evaluate the exposure level of each subject. Furthermore, Distributed lag non-linear models (DLNMs) were applied for statistic analysis.

RESULTS

The risk of child hyperactivity was found to be positively associated with early life exposure to PM₁₀, PM_2.5 and NO₂. In particular, for an increase of per 10 µg/m³ in PM₁₀, PM_2.5 and NO₂ exposure concentration during early life, the risk of child hyperactivity increased significantly during the seventh month of pregnancy to the fourth month after birth, with the strongest association in the ninth month of pregnancy (PM₁₀: OR = 1.043, 95% CI: 1.016-1.071; PM_2.5: OR = 1.062, 95% CI: 1.024-1.102; NO₂: OR = 1.043, 95% CI: 1.016-1.071). However, no significant associations among early life exposure to CO, O₃ and SO₂ and child hyperactive behaviors were observed.

CONCLUSIONS

Early life exposure to PM₁₀, PM_2.5 and NO₂ is associated with an increased risk of child ADHD-like behaviors at the age around 3 years, and the late-prenatal and early postnatal periods might be the susceptible exposure windows.

Associations between seasonal ambient air pollution and adverse perinatal outcomes: a retrospective cohort study in Wenzhou, China

Prenatal exposure to ambient air pollution has been associated with adverse perinatal outcomes in previous studies. However, few studies have examined the interaction between air pollution and the season of conception on term low birth weight (TLBW) or macrosomia. Birth registry data of singleton live births in Wenzhou, China, between January 2015 and December 2016 were accessed from the Wenzhou Maternal and Child Health Information Management platform, and data on the ambient air pollutants in Wenzhou were obtained from the Chinese Air Quality Online Monitoring and Analysis Platform. Single-/two-pollutant binary logistic regression models were used to assess the associations between ambient air pollutants (PM_2.5, PM₁₀, NO₂, SO₂, and O₃) and TLBW/macrosomia, further exploring whether the season of conception interacts with air pollution to impact birth weight. Finally, 213,959 term newborns were selected, including 2452 (1.1%) infants with TLBW and 13,173 (6.1%) infants with macrosomia. In the single-/two-pollutant models, we observed an increased risk of TLBW associated with maternal exposure to PM_2.5, PM₁₀, SO₂, and NO₂ during the entire pregnancy, especially in the 2nd trimester. Maternal exposure to O₃ during the 1st trimester was associated with increased macrosomia risk, and O₃ exposure during the 3rd trimester was associated with increased TLBW risk. Pregnant women who conceive in the warm season may experience a more adverse ambient air environment that is related to the risks of TLBW. These findings add to the evidence suggesting that air pollution and the season of conception may have synergistic effects on adverse perinatal outcomes, especially TLBW. Further prospective cohort studies are needed to validate our results.

Mother-level random effect in the association between PM2.5 and fetal growth: A population-based pregnancy cohort

BACKGROUND

A growing body of literature reports associations between exposure to particulate matter with diameter ≤2.5 μm (PM_2.5) during pregnancy and birth outcomes. However, findings are inconsistent across studies.

OBJECTIVES

To assess the association between PM_2.5 and birth outcomes of fetal growth in a cohort with high prevalence of siblings by multilevel models accounting for geographical- and mother-level correlations.

METHODS

In Israel, we used Maccabi Healthcare Services data to establish a population-based cohort of 381,265 singleton births reaching 24-42 weeks' gestation and birth weight of 500-5000 g (2004-2015). Daily PM_2.5 predictions from a satellite-based spatiotemporal model were linked to the date of birth and maternal residence. We generated mean PM_2.5 values for the entire pregnancy and for exposure periods during pregnancy. Associations between exposure and birth outcomes were modeled by using multilevel logistic regression with random effects for maternal locality of residence, administrative census area (ACA) and mother.

RESULTS

In fully adjusted models with a mother-level random intercept only, a 10-μg/m³ increase in PM_2.5 over the entire pregnancy was positively associated with term low birth weight (TLBW) (Odds ratio, OR = 1.25, 95% confidence interval, CI: 1.09,1.43) and small for gestational age (SGA) (OR = 1.15, 95% CI: 1.06,1.26). Locality- and ACA-level effects accounted for <0.4% of the variance while mother-level effects explained ∼50% of the variability. Associations varied by exposure period, infants' sex, birth order, and maternal pre-pregnancy BMI.

CONCLUSIONS

Consideration of mother-level variability in a region with high fertility rates provides new insights on the strength of associations between PM_2.5 and birth outcomes.

Association of exposure to fine particulate matter wave over the preconception and pregnancy periods with adverse birth outcomes: Results from the project ELEFANT

BACKGROUND

No study has explored the effects of sustained maternal exposure to high-level ambient fine particulate matter (PM_2.5) within a short period, i.e., PM_2.5 wave, on adverse birth outcomes, though increasing epidemiological studies demonstrated that exposure to single days of high ambient PM_2.5 could increase risks of adverse birth outcomes. In this study, we aim to evaluate associations of maternal PM_2.5 wave exposure around pregnancy with preterm birth (PTB), small for gestational age (SGA), and large for gestational age (LGA).

METHODS

Totally 10,916 singleton pregnant women from all 16 districts in Tianjin, China, and their followed-up birth outcomes were included in this study. We defined PM_2.5 wave as at least 2 consecutive days with daily average PM_2.5 concentration exceeding 75 μg/m³, and 90th, 92.5th, 95th, 97.5th, 99th percentiles of PM_2.5 distribution during the study period in Tianjin, respectively. Cox proportional hazard model was applied to evaluate the durational effects of PM_2.5 wave during each exposure window on PTB, SGA, and LGA after adjusting for potential confounders.

RESULTS

Exposure to PM_2.5 wave over the preconception and pregnancy periods was associated with increased risks of adverse birth outcomes. For PTB, the strongest association was found during the first trimester when PM_2.5 wave was defined as at least 4 consecutive days with daily average PM_2.5 concentration >90th (HR, 10.46; 95% CI, 6.23-17.54); and for SGA (HR, 6.23; 95% CI, 3.34-11.64) and LGA (HR, 4.70; 95% CI, 3.35-6.59), the strongest associations both were found when PM_2.5 wave was defined as at least 2 consecutive days with daily average PM_2.5 concentration >99th. Additionally, the risks of adverse birth outcomes generally increased at higher PM_2.5 thresholds or longer durations of PM_2.5 wave.

CONCLUSION

Prolonged exposure to high-level PM_2.5 over preconception and pregnancy periods was associated with increasing risks of PTB, SGA and LGA.

Association between Maternal Exposure to Ambient Air Pollution and the Risk of Preterm Birth: A Birth Cohort Study in Chongqing, China, 2015-2020

Recent study results on the association between maternal exposure to ambient air pollution with preterm birth have been inconsistent. The sensitive window of exposure and influence level of air pollutants varied greatly. We aimed to explore the association between maternal exposure to ambient air pollutants and the risk of preterm birth, and to estimate the sensitive exposure time window. A total of 572,116 mother–newborn pairs, daily concentrations of air pollutants from nearest monitoring stations were used to estimate exposures for each participant during 2015–2020 in Chongqing, China. We applied a generalized additive model and estimated RRs and 95% CIs for preterm birth in each trimester and the entire pregnancy period. In the single-pollutant model, we observed that each 10 μg/m³ increase in PM_2.5 had a statistically significant effect on the third trimester and entire pregnancy, with RR = 1.036 (95% CI: 1.021, 1.051) and RR = 1.101 (95% CI: 1.075, 1.128), respectively. Similarly, for each 10 μg/m³ increase in PM₁₀, there were 2.7% (RR = 1.027, 95% CI: 1.016, 1.038) increase for PTB on the third trimester, and 3.8% (RR = 1.038, 95% CI: 1.020, 1.057) increase during the whole pregnancy. We found that for each 10 mg/m³ CO increases, the relative risk of PTB increased on the first trimester (RR = 1.081, 95% CI: 1.007, 1.162), second trimester (RR = 1.116, 95% CI: 1.035, 1.204), third trimester (RR = 1.167, 95% CI: 1.090, 1.250) and whole pregnancy (RR = 1.098, 95% CI: 1.011, 1.192). No statistically significant RR was found for SO₂ and NO₂ on each trimester of pregnancy. Our study indicates that maternal exposure to high levels of PM_2.5 and PM₁₀ during pregnancy may increase the risk for preterm birth, especially for women at the late stage of pregnancy. Statistically increased risks of preterm birth were associated with CO exposure during each trimester and entire pregnancy. Reducing exposure to ambient air pollutants for pregnant women is clearly necessary to improve the health of infants.

Air pollution and preterm birth: A time-stratified case-crossover study in the San Joaquin Valley of California

BACKGROUND

Air pollution is linked to preterm birth (PTB), but existing studies are primarily focused on chronic exposures, conducted in areas with moderate pollution, and/or subject to confounding.

OBJECTIVES

We investigated short-term associations between two pollutants [particulate matter <2.5 microns (PM_2.5 ) and ozone] and PTB, and estimated excess PTB cases potentially attributed to these pollutants.

METHODS

This time-stratified case-crossover study includes 196,970 singleton pregnancies affected by PTB and early term birth from the San Joaquin Valley (SJV), California, USA (2007-2015). Daily ozone and PM_2.5 concentrations were estimated by the SJV Air Pollution Control District and geospatially linked to maternal zip code. We used conditional logistic regression models to estimate the odds ratio (OR) and 95% confidence intervals (CI) for the associations between an interquartile range (IQR) increase in pollutants and very preterm (VPTB, 20-34 weeks), moderate preterm (MPTB, 34-36 weeks) and early term births (ETB, 37-38 weeks). We adjusted all models for co-pollutants and meteorological factors.

RESULTS

During warm seasons (May-October), an IQR increase in ozone was associated with 9-11% increased odds of VPTB from lag 0 (OR_lag0 1.09, 95% CI 1.04,1.16) to lag 7 (OR_lag7 1.11, 95% CI 1.04,1.16). Findings were consistent for MPTB and ETB. Ozone was potentially responsible for an excess of 3-6 VPTBs, 7-9 PTBs and 24-42 ETBs per 1,000 singleton deliveries. During cold seasons (November-April), increased PM_2.5 exposure was associated with 5-6% increased odds of VPTB beginning at lag 3 (OR_lag3 1.06, 95% CI 1.02,1.11). PM_2.5 was associated with an excess of 1-3 VPTBs, 0-3 MPTBs and 6-18 ETBs per 1,000 singleton deliveries.

CONCLUSIONS

PM_2.5 and ozone are associated with increased risk of VPTB, MPTB and ETB within one week of exposure and are potential contributors to the increasing PTB trend. More research is needed to further understand the role of air pollution on PTB risk.

Retraction Note to: Ambient air pollution and adverse birth outcomes: a systematic review and meta-analysis

Retraction Note to: J Zhejiang Univ-Sci B (Biomed & Biotechnol) 2019 20(3):238-252. https://doi.org/10.1631/jzus.B1800122. The authors have retracted this article (Guo et al., 2019) because some data from the original literature had not been converted to appropriate units in the paper, which resulted in deviation of the meta-analysis results. For example, for the forest plot used to examine associations between PM₁₀ exposure and the risk of adverse birth outcomes, the estimates from Brauer et al. (2008), Pedersen et al. (2013), Zhao et al. (2015), and Hansen et al. (2006) were on the originally reported scales of 1 µg/m³, 10 µg/m³, 10 µg/m³, and Inter Quartile Range, respectively. None of these estimates had been converted to 20 µg/m³ increase scale that was stated in the article. Similar problem exists in the analysis on associations between NO₂ exposure and risk of adverse birth outcomes. Therefore, the results of the meta-analysis are misleading. All authors have agreed to this retraction and express their deepest apologies to the original authors, publishers, and readers.

Ozone exposure during early pregnancy and preterm birth: A systematic review and meta-analysis

Exposure to ozone has been linked to reproductive outcomes, including preterm birth. In this systematic review, we summarize published epidemiologic cohort and case-control studies examining ozone exposures (estimated on a continuous scale) in early pregnancy (1st and 2nd trimesters (T1, T2)) and preterm birth using ratio measures, and perform a meta-analysis to evaluate the potential relationship between them. Studies were identified by searching PubMed and Web of Science, screened according to predefined inclusion/exclusion criteria, and evaluated for study quality. We extracted study data including effect estimates, confidence limits, study location, study years, ozone exposure assessment method, and mean or median ozone concentrations. Nineteen studies were identified and included, of which 18 examined T1 exposure (17 reported effect estimates), and 15 examined T2 exposure. Random effects meta-analysis was performed in the metafor package, R 3.5.3. The pooled OR (95% CI) for a 10 ppb increase in ozone exposure in T1 was 1.06 (1.03, 1.10) with a 95% prediction interval of 0.95, 1.19; for T2 it was 1.05 (1.02, 1.08) with a 95% prediction interval of 0.95, 1.16. Effect estimates for both exposure periods showed high heterogeneity. In meta-regression analyses of study characteristics, study location (continent) explained some (~20%) heterogeneity for T1 exposure studies, but no characteristic explained a substantial amount of heterogeneity for T2 exposure studies. Increased ozone exposure during early pregnancy is associated with preterm birth across studies.

Exposure to ambient particulate matter and biomass burning during pregnancy: associations with birth weight in Thailand

BACKGROUND

There is a growing evidence that exposure to ambient particulate air pollution during pregnancy is associated with adverse birth outcomes, including reduced birth weight (BW). The objective of this study was to quantify associations between BW and exposure to particulate matter (PM) and biomass burning during pregnancy in Thailand.

METHODS

We collected hourly ambient air pollutant data from ground-based monitors (PM with diameter of <10 µm [PM₁₀], Ozone [O₃], and nitrogen dioxide [NO₂]), biomass burning from satellite remote sensing data, and individual birth weight data during 2015-2018. We performed a semi-ecological analysis to evaluate the association between mean trimester exposure to air pollutants and biomass burning with BW and low-birth weight (LBW) (<2500 g), adjusting for gestation age, sex, previous pregnancies, mother's age, heat index, season, year, gaseous pollutant concentrations, and province. We examined potential effect modification of PM₁₀ and biomass burning exposures by sex.

RESULTS

There were 83,931 eligible births with a mean pregnancy PM₁₀ exposure of 39.7 µg/m³ (standard deviation [SD] = 7.7). The entire pregnancy exposure was associated with reduced BW both for PM₁₀ (-6.81 g per 10 µg/m³ increase in PM₁₀ [95% CI = -12.52 to -1.10]) and biomass burning (-6.34 g per 1 SD increase in fires/km² [95% CI = -11.35 to -1.34]) only after adjustment for NO₂. In contrast with these findings, a reduced odds ratio (OR) of LBW was associated with PM₁₀ exposure only in trimesters one and two, with no relationship across the entire pregnancy period. Associations with biomass burning were limited to increased ORs of LBW with exposure in trimester three, but only for male births.

CONCLUSION

Based on our results, we encourage further investigation of air pollution, biomass burning and BW in Thailand and other low-income and middle-income countries.

Preterm birth among pregnant women living in areas with high social vulnerability

BACKGROUND

Communities and individuals widely vary in their resources and ability to respond to external stressors and insults. To identify vulnerable communities, the Centers for Disease Control and Prevention developed the Social Vulnerability Index, an integrated tool to assess community resources and preparedness; it is based on 15 factors and includes individual scores in the following 4 themes: socioeconomic status (theme 1), household composition and disability (theme 2), minority status and language (theme 3), and housing type and transportation (theme 4) and an overall composite score. Several Social Vulnerability Index components have been independently associated with an increased risk of preterm birth.

OBJECTIVE

We sought to investigate the association of the Social Vulnerability Index for each patient's residence during pregnancy, personal clinical risk factors, and preterm birth.

STUDY DESIGN

This was a retrospective cohort study of women carrying nonanomalous singleton or twin gestations delivering at a large university health system from April 2014 to January 2020. Women at high risk of spontaneous and medically indicated preterm birth were assigned to a census tract based on their geocoded home address, and a Social Vulnerability Index score was assigned to each individual by linking each patient's home address at the census tract level. Higher scores indicate greater social vulnerability. The primary outcome was preterm birth at <37 weeks' gestation; secondary outcomes were preterm birth at <34 and <28 weeks' gestation and composite major neonatal morbidity before initial hospital discharge (death, intraventricular leukomalacia or intraventricular hemorrhage, necrotizing enterocolitis, or bronchopulmonary dysplasia). Data were analyzed using the chi-square test, t test, and backward stepwise logistic regression. In addition, because race is a social construct, we conducted regression models omitting Black race. For all regression models, independent variables with a P value of <.20 remained in the final models.

RESULTS

Overall, 15,364 women met the inclusion criteria, of which 18.5%, 6.5%, 2.1% of women delivered at <37, <34, and <28 weeks' gestation, respectively, and 3.1% of neonates were diagnosed with major composite morbidity. Women delivering before term at <37, <34, and <28 weeks' gestation were more likely to live in an area with a higher overall Social Vulnerability Index and higher social vulnerability in each Social Vulnerability Index theme. In regression models, the adjusted odds ratio of preterm birth increased with increasing Social Vulnerability Index scores (across all themes and the composite value); these effects were the greatest at the earliest gestational ages (eg, for the composite Social Vulnerability Index: adjusted odds ratio of preterm birth at <37 weeks' gestation for models, including Black race, 1.32 [95% confidence interval, 1.14-1.53]; adjusted odds ratio at <34 weeks' gestation, 1.60 [95% confidence interval, 1.27-2.01]; adjusted odds ratio at <28 weeks' gestation, 2.21 [95% confidence interval, 1.50-3.25]; adjusted odds ratio for composite major neonatal morbidity, 2.30 [95% confidence interval, 1.67-3.17]). Similar trends were seen for each Social Vulnerability Index theme. In addition, an increased adjusted odds ratio of composite major neonatal morbidity was recognized for each Social Vulnerability Index theme. Results were similar when Black race was removed from the models.

CONCLUSION

The Social Vulnerability Index is a valuable tool that may further identify communities and individuals at the highest risk of preterm birth and may enable clinicians to integrate information regarding the local home environment of their patients to further refine preterm birth risk assessment.

Association between moderated level of air pollution and fetal growth: the potential role of noise exposure

This study aims to analyze, in a population of singletons, the potential confounding or modifying effect of noise on the relationship between fetal growth restriction (FGR) or small for gestational age (SGA) and environmental exposure to air pollution. All women with single pregnancies living in one of two medium-sized cities (Besançon, Dijon) and who delivered at a university hospital between 2005 and 2009 were included. FGR and SGA were obtained from medical records. Outdoor residential exposure to nitrogen dioxide (NO₂) and particulate matter (PM₁₀) was quantified at the mother’s address at delivery over defined pregnancy periods; outdoor noise exposure was considered to be the annual average daily noise levels in the façade of building (L_{Aeq,24 h}). Adjusted odds ratios (OR_a) were estimated by multivariable logistic regressions. Among the 8994 included pregnancies, 587 presented FGR and 918 presented SGA. In the two-exposure models, for SGA, the OR_a for a 10-µg/m³ increase of PM₁₀ during the two last months before delivery was 1.18, 95%CI 1.00–1.41 and for FGR, these OR_a were for the first and the third trimesters, and the two last months before delivery: 0.77 (0.61–0.97), 1.38 (1.12–1.70), and 1.35 (1.11–1.66), respectively. Noise was not associated with SGA or FGR and did not confound the relationship between air pollution and SGA or FGR. These results are in favor of an association between PM₁₀ exposure and fetal growth, independent of noise, particularly towards the end of pregnancy, and of a lack of association between noise and fetal growth.

Associations of adverse pregnancy outcomes with high ambient air pollution exposure: Results from the Project ELEFANT

BACKGROUND

Investigations on the potential effects of high air pollution exposure before pregnancy on adverse pregnancy outcomes are limited, and it is unknown whether air quality standards looser than that set by World Health Organization (WHO) still can provide sufficient protection pregnant women from adverse pregnancy outcomes.

OBJECTIVES

To evaluate the potential effects of high ambient air pollution around pregnancy on preterm birth (PTB) and low birth weight (LBW), and assess the risk of PTB and LBW associated with air pollutants with reference to different air quality standards of WHO and China.

METHODS

Our study leveraged 10,960 pregnant women from the Project ELEFANT. Daily average particulate matter with an aerodynamic diameter of ≤2.5 μm (PM_2.5) and ≤10 μm (PM₁₀), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), carbon monoxide (CO) and ozone (O₃) concentrations were collected based on Chinese Air Quality Reanalysis datasets. Hazard ratios (HR) of PTB and LBW were estimated for maternal PM_2.5, PM₁₀, NO₂, SO₂, CO and O₃ exposures and related proportions of days with daily average air pollution concentrations exceeding air quality standards of WHO and China around pregnancy using Cox proportional hazards regression models with adjustment for potential confounders.

RESULTS

Ambient PM_2.5, PM₁₀, NO₂, SO₂ and CO exposure during the before pregnancy and pregnancy period were both significantly and positively associated with increased risk of PTB, PTB subtypes and LBW. A 10% increase in proportion of days with daily average PM_2.5 exceeding 25 μg/m³ over the entire pregnancy was most apparently associated with risk of PTB (HR, 12.66; 95% CI, 8.20-19.53) and LBW (HR, 17.42; 95% CI, 6.88-44.10) among all PM_2.5 proportion variables based on different air quality standards.

CONCLUSION

Air quality standards of WHO are necessary to be implemented to control for risks of adverse pregnancy outcomes associated with ambient air pollution in areas with high air pollution levels.

Ambient BTEX exposure and mid-pregnancy inflammatory biomarkers in pregnant African American women

Air pollution is associated with preterm birth (PTB), potentially via inflammation. We recently showed the mixture benzene, toluene, ethylbenzene, and xylene (BTEX) is associated with PTB. We examined if ambient BTEX exposure is associated with mid-pregnancy inflammation in a sample of 140 African-American women residing in Detroit, Michigan. The Geospatial Determinants of Health Outcomes Consortium study collected outdoor air pollution measurements in Detroit; these data were coupled with Michigan Air Sampling Network measurements to develop monthly BTEX concentration estimates at a spatial density of 300 m². First trimester and mid-pregnancy BTEX exposure estimates were assigned to maternal address. Mid-pregnancy (mean 21.3 ± 3.7 weeks gestation) inflammatory biomarkers (high-sensitivity C-reactive protein, interleukin [IL]-6, IL-10, IL-1β, and tumor necrosis factor-α) were measured with enzyme immunoassays. After covariate adjustment, for every 1-unit increase in first trimester BTEX, there was an expected mean increase in log-transformed IL-1β of 0.05 ± 0.02 units (P = 0.014) and an expected mean increase in log-transformed tumor necrosis factor-α of 0.07 ± 0.02 units (P = 0.006). Similarly, for every 1-unit increase in mid-pregnancy BTEX, there was a mean increase in log IL-1β of 0.06 ± 0.03 units (P = 0.027). There was no association of either first trimester or mid-pregnancy BTEX with high-sensitivity C-reactive protein, IL-10, or IL-6 (all P > 0.05). Ambient BTEX exposure is associated with inflammation in mid-pregnancy in African-American women. Future studies examining if inflammation mediates associations between BTEX exposure and PTB are needed.

Gestational exposures to outdoor air pollutants in relation to low birth weight: A retrospective observational study

Findings for impacts of outdoor air pollutants on birth outcomes were controversial. We performed a retrospective observational study in 2527 preschoolers of Shanghai, China and investigated associations of duration-averaged concentrations of outdoor sulphur dioxide (SO₂), nitrogen dioxide (NO₂), and particulate matter with an aerodynamic diameter ≤ 10 μm (PM₁₀) in different months and trimesters of gestation, with preterm birth (PB), low birth weight (LBW), term low birth weight (T-LBW), and small for gestational age (SGA). Daily concentrations of outdoor air pollutants were collected in each residence-located district. Parents reported health information. In the multivariate logistic regression analyses, exposures to outdoor NO₂ were consistently associated with the higher odds of LBW and T-LBW. These associations were generally stronger for early months than for later months of the gestation. Adjusted odds ratios generally were larger in multi-pollutant model than in single-pollutant model. Exposure to NO₂ in the first month of the gestation was significantly associated with T-LBW (adjusted OR, 95%CI: 1.91, 1.02-3.58 for increment of interquartile range (18.5 μg/m³); p-value = 0.044) in multi-pollutant model. This association was stronger in girls, renters, and children whose mothers ≥30 years-old, with household dampness-related exposures, and with parental smoking during pregnancy. Our results indicate that exposure to NO₂ during gestation perhaps is a risk factor for LBW and T-LBW, and effects of NO₂ exposures could be greater during early periods than during later periods of gestation.

Environmental Risk Factors and Health: An Umbrella Review of Meta-Analyses

Background: Environmental health is a growing area of knowledge, continually increasing and updating the body of evidence linking the environment to human health. Aim: This study summarizes the epidemiological evidence on environmental risk factors from meta-analyses through an umbrella review. Methods: An umbrella review was conducted on meta-analyses of cohort, case-control, case-crossover, and time-series studies that evaluated the associations between environmental risk factors and health outcomes defined as incidence, prevalence, and mortality. The specific search strategy was designed in PubMed using free text and Medical Subject Headings (MeSH) terms related to risk factors, environment, health outcomes, observational studies, and meta-analysis. The search was limited to English, Spanish, and French published articles and studies on humans. The search was conducted on September 20, 2020. Risk factors were defined as any attribute, characteristic, or exposure of an individual that increases the likelihood of developing a disease or death. The environment was defined as the external elements and conditions that surround, influence, and affect a human organism or population's life and development. The environment definition included the physical environment such as nature, built environment, or pollution, but not the social environment. We excluded occupational exposures, microorganisms, water, sanitation and hygiene (WASH), behavioral risk factors, and no-natural disasters. Results: This umbrella review found 197 associations among 69 environmental exposures and 83 diseases and death causes reported in 103 publications. The environmental factors found in this review were air pollution, environmental tobacco smoke, heavy metals, chemicals, ambient temperature, noise, radiation, and urban residential surroundings. Among these, we identified 65 environmental exposures defined as risk factors and 4 environmental protective factors. In terms of study design, 57 included cohort and/or case-control studies, and 46 included time-series and/or case-crossover studies. In terms of the study population, 21 included children, and the rest included adult population and both sexes. In this review, the largest body of evidence was found in air pollution (91 associations among 14 air pollution definitions and 34 diseases and mortality diagnoses), followed by environmental tobacco smoke with 24 associations. Chemicals (including pesticides) were the third larger group of environmental exposures found among the meta-analyses included, with 19 associations. Conclusion: Environmental exposures are an important health determinant. This review provides an overview of an evolving research area and should be used as a complementary tool to understand the connections between the environment and human health. The evidence presented by this review should help to design public health interventions and the implementation of health in all policies approach aiming to improve populational health.

The influence of industry-related air pollution on birth outcomes in an industrialized area

Recent studies suggests that air pollution, from among others road traffic, can influence growth and development of the human foetus during pregnancy. The effects of air pollution from heavy industry on birth outcomes have been investigated scarcely. Our aim was to investigate the associations of air pollution from heavy industry on birth outcomes. A cross-sectional study was conducted among 4488 singleton live births (2012-2017) in the vicinity of a large industrial area in the Netherlands. Information from the birth registration was linked with a dispersion model to characterize annual individual-level exposure of pregnant mothers to air pollutants from industry in the area. Associations between particulate matter (PM₁₀), nitrogen oxides (NO_X), sulphur dioxide (SO₂), and volatile organic compounds (VOC) with low birth weight (LBW), preterm birth (PTB), and small for gestational age (SGA) were investigated by logistic regression analysis and with gestational age, birth weight, birth length, and head circumference by linear regression analysis. Exposures to NO_X, SO₂, and VOC (per interquartile range of 1.16, 0.42, and 0.97 μg/m³ respectively) during pregnancy were associated with LBW (OR 1.20, 95%CI 1.06-1.35, OR 1.20, 95%CI 1.00-1.43, and OR 1.21, 95%CI 1.08-1.35 respectively). NO_X and VOC were also associated with PTB (OR 1.14, 95%CI 1.01-1.29 and OR 1.17, 95%CI 1.04-1.31 respectively). Associations between exposure to air pollution and birth weight, birth length, and head circumference were statistically significant. Higher exposure to PM₁₀, NO_X, SO₂ and VOC (per interquartile range of 0.41, 1.16, 0.42, and 0.97 μg/m³ respectively) was associated with reduced birth weight of 21 g to 30 g. The 90th percentile industry-related PM₁₀ exposure corresponded with an average birth weight decrease of 74 g.

Gaining a deeper understanding of social determinants of preterm birth by integrating multi-omics data

In the US, high rates of preterm birth (PTB) and profound Black-White disparities in PTB have persisted for decades. This review focuses on the role of social determinants of health (SDH), with an emphasis on maternal stress, in PTB disparity and biological embedding. It covers: (1) PTB disparity in US Black women and possible contributors; (2) the role of SDH, highlighting maternal stress, in the persistent racial disparity of PTB; (3) epigenetics at the interface between genes and environment; (4) the role of the genome in modifying maternal stress-PTB associations; (5) recent advances in multi-omics studies of PTB; and (6) future perspectives on integrating multi-omics with SDH to elucidate the Black-White disparity in PTB. Available studies have indicated that neither environmental exposures nor genetics alone can adequately explain the Black-White PTB disparity. Preliminary yet promising findings of epigenetic and gene-environment interaction studies underscore the value of integrating SDH with multi-omics in prospective birth cohort studies, especially among high-risk Black women. In an era of rapid advancements in biomedical sciences and technologies and a growing number of prospective birth cohort studies, we have unprecedented opportunities to advance this field and finally address the long history of health disparities in PTB. IMPACT: This review provides an overview of social determinants of health (SDH) with a focus on maternal stress and its role on Black-White disparity in preterm birth (PTB). It summarizes the available literature on the interplay of maternal stress with key biological layers (e.g., individual genome and epigenome in response to environmental stressors) and significant knowledge gaps. It offers perspectives that such knowledge may provide deeper insight into how SDH affects PTB and why some women are more vulnerable than others and underscores the critical need for integrating SDH with multi-omics in prospective birth cohort studies, especially among high-risk Black women.

Impact of air pollution exposure during various periods of pregnancy on term birth weight: a large-sample, retrospective population-based cohort study

Previous studies have suggested that maternal exposure to air pollution might affect term birth weight. However, the conclusions are controversial. Birth data of all term newborns born in Xi'an city of Shaanxi, China, from 2015 to 2018 and whose mother lived in Xi'an during pregnancy were selected form the Birth Registry Database. And the daily air quality data of Xi'an city was collected from Chinese Air Quality Online Monitoring and Analysis Platform. Generalized additive models (GAM) and 2-level binary logistic regression models were used to estimate the effects of air pollution exposure on term birth weight, the risk term low birth weight (TLBW), and macrosomia. Finally, 321521 term newborns were selected, including 4369(1.36%) TLBW infants and 24,960 (7.76%) macrosomia. The average pollution levels of PM_2.5, PM₁₀, and NO₂ in Xi'an city from 2015 to 2018 were higher than national limits. During the whole pregnancy, maternal exposure to PM_2.5, PM₁₀, SO₂, and CO all significantly reduced the term birth weight and increased the risk of TLBW. However, NO₂ and O₃ exposure have significantly increased the term birth weight, and O₃ even increased the risk of macrosomia significantly. Those effects were also observed in the first and second trimesters of pregnancy. But during the third trimester, high level of air quality index (AQI) and maternal exposure to PM_2.5, PM₁₀, SO₂, NO₂, and CO increased the term birth weight and the risk of macrosomia, while O₃ exposure was contrary to this effect. The findings suggested that prenatal exposure to air pollution might cause adverse impacts on term birth weight, and the effects varied with trimesters and pollutants, which provides further pieces of evidence for the adverse effects of air pollution exposure in heavy polluted-area on term birth weight.

Review of epidemiological studies on air pollution and health effects in children

There is a growing body of literature on the adverse health effects of ambient air pollution. Children are more adversely affected by air pollution due to their biological susceptibility and exposure patterns. This review summarized the accumulated epidemiologic evidence with emphasis on studies conducted in Korea and heterogeneity in the literature. Based on systematic reviews and meta-analyses, there is consistent evidence on the association between exposure to ambient air pollution and children's health, especially respiratory health and adverse birth outcomes, and growing evidence on neurodevelopmental outcomes. Despite these existing studies, the mechanism of the adverse health effects of air pollution and the critical window of susceptibility remain unclear. There is also a need to identify causes of heterogeneity between studies in terms of measurement of exposure/outcome, study design, and the differential characteristics of air pollutants and population.

In Utero Exposure to Particulate Air Pollution during Pregnancy: Impact on Birth Weight and Health through the Life Course

In high-income countries, and increasingly in lower- and middle-income countries, chronic non-communicable diseases (NCDs) have become the primary health burden. It is possible that in utero exposure to environmental pollutants such as particulate matter (PM) may have an impact on health later in life, including the development of NCDs. Due to a lack of data on foetal growth, birth weight is often used in epidemiologic studies as a proxy to assess impacts on foetal development and adverse birth outcomes since it is commonly recorded at birth. There are no research studies with humans that directly link PM exposure in utero to birth weight (BW) and subsequently, the effects of lower BW on health outcomes in old age. It is, however, plausible that such associations exist, and it is thus important to assess the potential public health impacts of PM across the life course, and it is plausible to use birth weight as an indicator of risk. We therefore split this narrative review into two parts. In the first part, we evaluated the strength of the evidence on the impact of PM exposure during the entire pregnancy on birth weight outcomes in ten meta-analyses. In the second part, we reviewed the literature linking lower birth weight to childhood and adult chronic cardiovascular disease to explore the potential implications of PM exposure in utero on health later in life. Within the reviewed meta-studies on birth weight, there is sufficient evidence that PM pollution is associated with lower birth weight, i.e., the majority of meta-studies found statistically significant reductions in birth weight. From the second part of the review, it is evident that there is good evidence of associations between lower birth weight and subsequent cardiovascular disease risk. It is thus plausible that in utero exposure to PM is associated with lower birth weight and persisting biological changes that could be associated with adverse health effects in adulthood. Based on the reviewed evidence, however, the magnitude of later life cardiovascular health impacts from in utero exposure and its impact on BW are likely to be small compared to health effects from exposure to particulate air pollution over a whole lifetime.

Ambient Air Pollution, Extreme Temperatures and Birth Outcomes: A Protocol for an Umbrella Review, Systematic Review and Meta-Analysis

Prenatal exposure to ambient air pollution and extreme temperatures are among the major risk factors of adverse birth outcomes and with potential long-term effects during the life course. Although low- and middle-income countries (LMICs) are most vulnerable, there is limited synthesis of evidence in such settings. This document describes a protocol for both an umbrella review (Systematic Review 1) and a focused systematic review and meta-analysis of studies from LMICs (Systematic Review 2). We will search from start date of each database to present, six major academic databases (PubMed, CINAHL, Scopus, MEDLINE/Ovid, EMBASE/Ovid and Web of Science Core Collection), systematic reviews repositories and references of eligible studies. Additional searches in grey literature will also be conducted. Eligibility criteria include studies of pregnant women exposed to ambient air pollutants and/or extreme temperatures during pregnancy with and without adverse birth outcomes. The umbrella review (Systematic Review 1) will include only previous systematic reviews while Systematic Review 2 will include quantitative observational studies in LMICs. Searches will be restricted to English language using comprehensive search terms to consecutively screen the titles, abstracts and full-texts to select eligible studies. Two independent authors will conduct the study screening and selection, risk of bias assessment and data extraction using JBI SUMARI web-based software. Narrative and semi-quantitative syntheses will be employed for the Systematic Review 1. For Systematic Review 2, we will perform meta-analysis with two alternative meta-analytical methods (quality effect and inverse variance heterogeneity) as well as the classic random effect model. If meta-analysis is infeasible, narrative synthesis will be presented. Confidence in cumulative evidence and the strength of the evidence will be assessed. This protocol is registered with PROSPERO (CRD42020200387).

Maternal exposure to air pollution and the risk of low birth weight: A meta-analysis of cohort studies

Previous studies have evaluated the relationship between prenatal air pollution exposure and low birth weight, but the results are inconsistent. The purpose of this meta-analysis is to quantitatively analyze the relationship between maternal air pollutant exposure and low birth weight (LBW). PubMed and Web of Science databases were searched to obtain the studies on the relationship between the prenatal exposure of air pollutants and LBW that published as of June 2020. The pooled effects of air pollutant exposure and LBW were calculated using random-effect model (for studies with significant heterogeneity) or fixed-effect model (for studies without significant heterogeneity). Totally, 54 studies were included in this meta-analysis. The pooled effect of PM_2.5, PM₁₀, NO₂, CO, SO₂, and O₃ exposure on LBW were 1.081 (95% CI: 1.043, 1.120), 1.053 (95% CI: 1.030, 1.076), 1.030 (95% CI: 1.008, 1.053), 1.007 (95% CI: 1.001, 1.014), 1.125 (95% CI: 1.017, 1.244), and 1.045 (95% CI: 1.005, 1.086), respectively. NO₂ (per 10 ppb increase) and CO (per 100 ppb increase) exposure in the first trimester were positively correlated with LBW, of which the pooled effect was 1.022 (95% CI: 1.009, 1. 035) and 1.008 (95% CI: 1.004, 1.012), respectively. PM_2.5 (per 10 μg/m³ increase) exposure in the third trimester significantly affected the LBW, of which the pooled effect was 1.053 (95% CI: 1.010, 1.097). In addition, PM₁₀ (per 10 μg/m³ increase) exposure in the second trimester also significantly affected the LBW, with the pooled effect of 1.011 (95% CI: 1.005, 1.017). Prenatal exposure of the major air pollutants during the entire pregnancy could increase the risk of LBW, while the susceptible window of the pollutants varied.

Nitrogen dioxide exposure during pregnancy and risk of spontaneous abortion: a case-control study in China

BACKGROUND

Evidence on the relationship between prenatal exposure to NO₂ and CO and spontaneous abortion (SAB) is insufficient. We investigated whether there is an association between maternal exposure to nitrogen dioxide (NO₂) and carbon monoxide (CO) before and during pregnancy and SAB.

METHODS

We conducted a case-control study using medical records of 2445 pregnant women who admitted for abortion prior to 20 weeks of gestational age from January 2014 to December 2019 at a tertiary-care hospital in Shanghai, China. Of the 2445 participants, 1075 were SAB cases and 1370 were healthy controls (underwent elective abortions). Maternal exposure to NO₂ and CO before and during pregnancy was estimated using daily air pollution concentration data. Multivariable logistic regression models were constructed to quantify the relationships between maternal exposure to NO₂ or CO and the risk of SAB while controlling for potential confounders.

RESULTS

NO₂ exposure levels during pregnancy were significantly higher in SAB cases than in healthy controls (42.26 vs. 40.67, p < .01). NO₂ exposure during pregnancy was positively associated with the risk of SAB. An interquartile range (16 μg/m³) increase in NO₂ exposure was associated with 68% increase in the odds of SAB (OR = 1.68, 95% CI, 1.28, 2.21). Analyses of associations by quartile of NO₂ exposure showed that elevated NO₂ exposure during pregnancy was associated with increased odds of SAB in linear dose-response manners. Compared with the lowest quartile of NO₂ exposure, the odds of SAB in the fourth quartile of NO₂ exposure increased 61% (OR = 1.61, 95% CI, 1.03-2.53). No associations of CO exposure with SAB risk were observed.

CONCLUSIONS

Our study suggested that exposure to NO₂ during early pregnancy was associated with increased risk of SAB. Further studies are needed to confirm our results and explore the potential biological mechanism underlying these associations.

Measuring Burden of Disease Attributable to Air Pollution Due to Preterm Birth Complications and Infant Death in Paris Using Disability-Adjusted Life Years (DALYs)

Several studies have found maternal exposure to particulate matter pollution was associated with adverse birth outcomes, including infant mortality and preterm birth. In this context, our study aims to quantify the air pollution burden of disease due to preterm birth complications and infant death in Paris, with particular attention to people living in the most deprived census blocks. Data on infant death and preterm birth was available from the birth and death certificates. The postal address of mother’s newborn was converted in census block number. A socioeconomic deprivation index was built at the census block level. Average annual ambient concentrations of PM₁₀ were modelled at census block level using the ESMERALDA atmospheric modelling system. The number of infant deaths attributed to PM₁₀ exposure is expressed in years of life lost. We used a three-step compartmental model to appraise neurodevelopmental impairment among survivors of preterm birth. We estimated that 12.8 infant deaths per 100,000 live births may be attributable to PM₁₀ exposure, and about one third of these infants lived in deprived census blocks. In addition, we found that approximately 4.8% of preterm births could be attributable to PM₁₀ exposure, and approximately 1.9% of these infants died (corresponding to about 5.75 deaths per 100,000 live birth). Quantification of environmental hazard-related health impacts for children at local level is essential to prioritizing interventions. Our study suggests that additional effort is needed to reduce the risk of complications and deaths related to air pollution exposure, especially among preterm births. Because of widespread exposure to air pollution, significant health benefits could be achieved through regulatory interventions aimed at reducing exposure of the population as a whole, and particularly of the most vulnerable, such as children and pregnant women.

Prenatal airshed pollutants and preterm birth in an observational birth cohort study in Detroit, Michigan, USA

Detroit, Michigan, currently has the highest preterm birth (PTB) rate of large cities in the United States. Disproportionate exposure to ambient air pollutants, including particulate matter ≤2.5 μm (PM_2.5), PM ≤ 10 μm (PM₁₀), nitrogen dioxide (NO₂) and benzene, toluene, ethylbenzene, and xylenes (BTEX) may contribute to PTB. Our objective was to examine the association of airshed pollutants with PTB in Detroit, MI. The Geospatial Determinants of Health Outcomes Consortium (GeoDHOC) study collected air pollution measurements at 68 sites in Detroit in September 2008 and June 2009. GeoDHOC data were coupled with 2008-2010 Michigan Air Sampling Network measurements in Detroit to develop monthly ambient air pollution estimates at a spatial density of 300 m². Using delivery records from two urban hospitals, we established a retrospective birth cohort of births by Detroit women occurring from June 2008 to May 2010. Estimates of air pollutant exposure throughout pregnancy were assigned to maternal address at delivery. Our analytic sample size included 7961 births; 891 (11.2%) were PTB. After covariate adjustment, PM₁₀ (P = 0.003) and BTEX (P < 0.001), but not PM_2.5 (P = 0.376) or NO₂ (P = 0.582), were statistically significantly associated with PTB. In adjusted models, for every 5-unit increase in PM₁₀ there was a 1.21 times higher odds of PTB (95% CI 1.07, 1.38) and for every 5-unit increase in BTEX there was a 1.54 times higher odds of PTB (95% CI 1.25, 1.89). Consistent with previous studies, higher PM₁₀ was associated with PTB. We also found novel evidence that higher airshed BTEX is associated with PTB. Future studies confirming these associations and examining direct measures of exposure are needed.

Adverse birth outcomes in Victoria, Australia in association with maternal exposure to low levels of ambient air pollution

BACKGROUND

The relationship between maternal exposure to air pollution and birth outcomes is not well characterised where ambient air pollution is relatively low.

OBJECTIVES

We aimed to explore the association between maternal exposure to ambient nitrogen dioxide (NO₂) and fine particulate matter (PM_2.5) and a range of birth outcomes in Victoria, Australia. Secondary aims were to explore whether obstetric conditions, such as gestational diabetes mellitus (GDM) and hypertensive disorders of pregnancy, were effect modifiers in observed relationships.

METHODS

We included all singleton births occurring in Victoria, Australia from 1^st March 2012 to 31^st December 2015 using routinely collected government data. Outcomes included birth weight, small for gestational age (SGA), term low birth weight (tLBW), large for gestational age (LGA), and spontaneous preterm birth (sPTB). We estimated exposure to annual ambient NO₂ and PM_2.5 concentrations, assigned to maternal residence at time of birth. Confounders included maternal, meteorological and temporal variables. Multivariable linear regression and log-binomial regression were used for continuous and dichotomous outcomes, respectively.

RESULTS

There were 285,594 births during the study period. Average NO₂ exposure was 6.0 parts per billion (ppb, median 5.6; interquartile range (IQR) 3.9) and PM_2.5 was 6.9 μg/m³ (median 7.1, IQR 1.3). IQR increases in ambient NO₂ and PM_2.5 were associated with fetal growth restriction, including decrements in birth weight (NO₂ β -22.8 g; 95%CI -26.0, -19.7; PM_2.5 β -14.8 g; 95%CI -17.4, -12.2) and increased risk of SGA (NO₂ RR 1.08; 95%CI 1.06, 1.10; PM_2.5 RR 1.05; 95%CI 1.04, 1.07) and tLBW (NO₂ RR 1.06; 95%CI 1.01, 1.10; PM_2.5 RR 1.04; 95%CI 1.03, 1.08). Women with GDM and hypertensive disorders of pregnancy had greater decrements in birth weight in association with pollutant exposure.

DISCUSSION

In this exploratory study using an annual metric of exposure, maternal exposure to low-level ambient air pollution was associated with fetal growth restriction, which carries substantial public health implications.

Traffic-related metrics and adverse birth outcomes: A systematic review and meta-analysis

Given the inconsistency of epidemiologic evidence for associations between maternal exposures to traffic-related metrics and adverse birth outcomes, this manuscript aims to provide clarity on this topic. Pooled meta-estimates were calculated using random-effects analyses. Subgroup analyses were conducted by study area, study design, and Newcastle-Ottawa quality score (NOS). Funnel plots and Egger's test were conducted to evaluate the publication bias, and Fail-safe Numbers (Fail-safe N) were measured to evaluate the robustness of models. From the initial 740 studies (last search, July 11, 2019), 26 studies were included in our analysis. The pooled odds ratio for the change in small for gestational age associated with per 500 m decrease in the distance to roads was 1.016 (95% CI: 1.004, 1.029). Subgroup analyses revealed significant positive associations between term low birth weight and traffic density in higher-quality literatures with higher NOS [1.060 (95% CI: 1.002, 1.121)], cohort studies [1.020 (95% CI: 1.006, 1.033)], and studies in North America [1.018 (95% CI: 1.005, 1.131)]. The buffer of traffic density made no difference in the effect size. Traffic density seemed to be a better indicator of traffic pollution than the distance to roads.

The association between prenatal exposure to polycyclic aromatic hydrocarbons and birth weight: A meta-analysis

Background

Polycyclic aromatic hydrocarbons (PAHs) are a kind of endocrine disruptors, which can enter human body by the inhalation of PAH-containing matter and the ingestion of PAH-containing foodstuffs. Studies showed that PAHs can cross the placental barrier and might cause adverse effects on the fetus.

Objectives

This meta-analysis aimed to estimate the associations between prenatal exposure to PAHs and birth weight.

Methods

Articles published in English until May 8, 2020 and reported the effects of prenatal exposure to PAHs on birth weight were searched in multiple electronic databases including PubMed, the Web of Science, EMBASE and the Cochrane Library. The included studies were divided into three groups in accordance with the measurement of PAHs exposure. Then coefficient was extracted, conversed and synthesized by random-effects meta-analysis. And risk of bias was assessed for each study.

Results

A total of 3488 citations were searched and only 11 studies were included finally after double assessment. We found that there were no association between PAH-DNA adducts in cord blood (low/high) (OR: 1.0, 95%CI: 0.97, 1.03), 1-hydroxy pyrene (1-HP) concentration in maternal urine (OR: 1.0, 95%CI: 0.97, 1.03) and prenatal maternal airborne PAHs exposure (OR: 0.97, 95%CI: 0.93, 1.01) and birth weight. However, we observed ethnicity may change the effects of PAHs exposure on birth weight.

Conclusions

There is no significant relationship between prenatal exposure to PAHs and birth weight in our meta-analysis. Further studies are still needed for determining the effects of prenatal PAHs exposure on birth weight.

Interactions between Environmental Exposures and the Microbiome: Implications for Fetal Programming

Decades of population-based health outcomes data highlight the importance of understanding how environmental exposures in pregnancy affect maternal and neonatal outcomes. Animal model research and epidemiological studies have revealed that such exposures are able to alter fetal programming through stable changes in the epigenome, including altered DNA methylation patterns and histone modifications in the developing fetus and infant. It is similarly known that while microbes can biotransform environmental chemicals via conjugation and de-conjugation, specific exposures can also alter the community profile and function of the human microbiome. In this review, we consider how alterations to the maternal and or fetal/infant microbiome through environmental exposures could directly and indirectly alter fetal programming. We highlight two specific environmental exposures, cadmium (Cd) and polycyclic aromatic hydrocarbons (PAHs), and outline their effects on the developing fetus and the perinatal (maternal and fetal/infant) microbiome. We further consider how chemical exposures in the setting of natural disasters may be of particular importance to environmental health.

Influence of Environmental Tobacco Smoke and Air Pollution on Fetal Growth: A Prospective Study

Exposure to air pollution during pregnancy leads to adverse pregnancy outcomes. Few studies have evaluated the influences of air quality, including environmental tobacco smoke (ETS) and particulate matter (PM), on fetal development, which this study examined. This longitudinal correlation study used multiple linear regression data analysis of PM_2.5/PM₁₀, self-reported ETS exposure, urinary cotinine level, maternal characteristics, and birth parameters (gestational week, body weight, body length, head, and chest circumferences) with the effect of air quality on fetal growth. The study included 74 pregnant women (mean age 31.9 ± 4.2 years, body mass index 23.6 ± 3.8 kg/m², average gestational duration 38.5 ± 0.8 weeks). ETS exposure decreased birth length by ≥1 cm, and potentially is an independent risk factor for fetal growth restriction, and pregnant women should avoid indoor and outdoor ETS. However, neither PM_2.5/PM₁₀ nor ETS was associated with low birth weight or small for gestational age. This study adds to the evidence base that ETS exposure of nonsmoking pregnant women affects the fetal birth length. Family members should refrain from smoking near expectant mothers, although smoking in the vicinity of their residential surroundings potentially exposes mothers and their fetuses to ETS. Public pollution and childbirth education classes should include details of indoor ETS.

Testing the Multiple Pathways of Residential Greenness to Pregnancy Outcomes Model in a Sample of Pregnant Women in the Metropolitan Area of Donostia-San Sebastián

Residential greenness may positively impact diverse human health indicators through the reduction of air pollution, the improvement of psychological health, and the promotion of physical activity. Previous studies indicate a weak but positive association with pregnancy outcomes. Our aim was to test the multiple pathways from residential greenness to pregnancy outcomes model, using residential NO₂ concentrations, psychological health, and moderate-to-vigorous physical activity (MVPA) during the first trimester of pregnancy, in a sample of 440 pregnant women residing in Donostia, Spain. Three metrics of residential greenness were calculated around each participant’s home address: normalized difference vegetation index (NDVI) within 300 m, and green space (>5000 m²) availability within 300 and 500 m. Residential NO₂ concentrations, psychological health, and MVPA were explored as mediators of the associations between these metrics and the following pregnancy outcomes: birth weight (BW), low birth weight (LBW), prematurity, small for gestational age (SGA), and large for gestational age (LGA). Educational attainment, parity, and body mass index (BMI) were treated as covariates. Counterfactual mediation analyses showed very low to null statistical support for an association between any of the greenspace metrics and pregnancy outcomes in the full sample. Green space availability (300 m) was associated with lower BW and showed a marginal protective effect against LGA.

The associations of particulate matters with fetal growth in utero and birth weight: A birth cohort study in Beijing, China

BACKGROUND

Previous studies examined the associations of particulate matters (PM) with fetal growth in utero or birth weight with inconsistent results, and few studies investigated that whether the associations of PM with fetal growth in utero also present at birth. We aimed to investigate the associations of PM with both fetal growth in utero and birth weight.

METHODS

We established a birth cohort (2014-2017) with 18,863 singleton pregnancies in Tongzhou Maternal and Child Hospital of Beijing, China. Maternal exposure to PM with aerodynamic diameters ≤2.5 μm and ≤ 10 μm (PM_2.5/PM₁₀) during pregnancy was estimated using the inverse distance weighting method. Estimated birth weight (EFW) was assessed by ultrasound measurements and birth weight was measured at birth, which were both standardized as gestational-age- and gender-adjusted Z-score. EFW undergrowth, low birth weight (LBW) and small-for-gestational-age were defined as the categorized outcomes. Generalized estimating equations and generalized linear regression were used to examine the associations of PM with quantitative and categorized outcomes, controlling for temperature, greenspace and individual covariates.

RESULTS

A 10 μg/m³ increase in PM_2.5 and PM₁₀ were associated with lower EFW Z-score [-0.031, 95% confident interval (CI): -0.047, -0.016 and -0.030, 95% CI: -0.043, -0.017]. A 10 μg/m³ increase in PM_2.5 was associated with lower birth weight Z-score (-0.035, 95% CI: -0.061, -0.010) and higher risk of LBW (OR = 1.240, 95% CI: 1.019, 1.508). These results remained robust in co-pollutant models and sensitivity analyses. We didn't find significant results in other analyses.

CONCLUSIONS

The study identified an inverse association between PM and fetal growth in utero. The association between PM_2.5 and fetal growth persisted from pregnancy to birth. This study supported that further actions towards controlling air pollution are strongly recommended for promoting early-life health.

Adverse Birth Outcomes as Indicators of Poor Fetal Growth Conditions in a French Newborn Population-A Stratified Analysis by Neighborhood Deprivation Level

Background: Adverse birth outcomes are related to unfavorable fetal growth conditions. A latent variable, named Favorable Fetal Growth Condition (FFGC), has been defined by Bollen et al., in 2013; he showed that this FFGC latent variable mediates the effects of maternal characteristics on several birth outcomes. Objectives: The objectives of the present study were to replicate Bollen’s approach in a population of newborns in Paris and to investigate the potential differential effect of the FFGC latent variable according to the neighborhood socioeconomic level. Methods: Newborn health data were available from the first birth certificate registered by the Maternal and Child Care department of the City of Paris. All newborns (2008–2011) were geocoded at the mother residential census block. Each census block was assigned a socioeconomic deprivation level. Several mothers’ characteristics were collected from the birth certificates: age, parity, education and occupational status and the occupational status of the father. Three birth outcomes were considered: birth weight (BW), birth length (BL) and gestational age (GA). Results: Using a series of structural equation models, we confirm that the undirected model (that includes the FFGC latent variable) provided a better fit for the data compared with the model where parental characteristics directly affected BW, BL, and/or GA. However, the strength, the direction and statistical significance of the associations between the exogenous variables and the FFGC were different according to the neighborhood deprivation level. Conclusion: Future research should be designed to assess the how robust the FFGC latent variable is across populations and should take into account neighborhood characteristics to identify the most vulnerable group and create better design prevention policies.

Prenatal ambient air pollution exposure and SOD2 promoter methylation in maternal and cord blood

The evidence is increasing that prenatal air pollutant exposure contributes to elevated oxidative stress in children, but the underlying mechanism is unclear. A pilot study was conducted in China to explore the associations between prenatal ambient air pollution exposure and superoxide dismutase 2 (SOD2) promoter methylation in maternal and cord blood. After detection and analyses, SOD2 promoter methylation levels in umbilical cord blood were elevated as maternal SOD2 promoter methylation levels increased. In addition, the SOD2 promoter methylation levels in umbilical cord blood were positively associated with the particulate matter 10 (PM₁₀) exposure concentrations during the entire pregnancy and the second trimester. In maternal peripheral blood, the SOD2 promoter methylation levels were positively associated with the exposure concentrations of PM₁₀ (during the entire pregnancy and the second trimester) and nitrogen dioxide (NO₂) (during the first trimester of pregnancy), whereas the levels were negatively associated with the exposure concentrations of NO₂ during the third trimester of pregnancy. Additionally, interaction analyses revealed that the maternal SOD2 promoter methylation level and sulfur dioxide (SO₂) exposure (during the entire pregnancy and the third trimester), as well as NO₂ exposure (during the third trimester of pregnancy), had an interaction effect on the SOD2 promoter methylation level in umbilical cord blood. Furthermore, mediation analysis revealed that the associations between SOD2 promoter methylation in umbilical cord blood and PM₁₀ exposure during the entire pregnancy and the second trimester were partly mediated by maternal SOD2 promoter methylation. In conclusion, prenatal exposure to air pollutants was significantly associated with SOD2 promoter methylation levels in umbilical cord blood, and this association may be affected by SOD2 promoter methylation levels in maternal peripheral blood. These associations may be one of the mechanisms by which prenatal air pollutant exposure leads to oxidative stress in newborns.